Thermodynamic and heat transfer analysis of hydrogen-fueled meso-scale combustors with tear-drop structures for thermophotovoltaic applications

In this work, tear-drop protrusion (TDP) and tear-drop dimple (TDD) structures are proposed for the design of meso-scale combustors implemented for thermophotovoltaic (TPV) applications. The research examines and contrasts their thermal performance and internal flow heat transfer characteristics to evaluate the performance improvement of the new structural combustor. The TDP structure is confirmed to demonstrate a better ability to elevate the combustor wall temperature at higher inlet velocities (Vin), with a higher internal flow resistance, thus enhancing heat transfer. However, this also resulted in a higher pressure loss (Ploss). At a lower Vin, the improvement in the combustor wall temperature uniformity is more pronounced. Additionally, increasing Vin is found to enhance the combustor's thermal performance. When the equivalence ratio (Φ) is set to around 1, the fuel's heat release inside the combustor is maximized, along with the highest Ploss. Finally, the combustor exhibited superior convective heat transfer performance, when Φ is ranged between 0.8 and 0.9. The TDP structure thus exhibited stronger advection effects compared to the TDD structure, while the TDD demonstrated superior diffusion performance. This enhanced diffusion capability of TDD facilitated better fuel-air mixing under conditions of insufficient air at high Φ values, thereby improving combustion efficiency (ηcombustion).